Chapter 3) Movement in and out of cells

Diffusion

movement of particles from a region of high concentration to a region of low concentration down a concentration gradient (no energy required)

Concentration gradient

difference in concentration between two areas

Passive transport

movement of substances without using energy

Osmosis

movement of water molecules through a partially permeable membrane from a region of higher water concentration (dilute solution) to lower water concentration (concentrated solution)

Partially permeable membrane

allows some substances (like water) to pass through but not others

Active transport

movement of substances from low to high concentration against a concentration gradient using energy (ATP)

ATP

energy released from respiration used for active transport

Factors affecting diffusion

temperature (higher = faster), surface area (larger = faster), concentration gradient (steeper = faster), distance (shorter = faster)

Surface area to volume ratio

ratio that determines how efficiently substances can enter or leave a cell

Gas exchange

movement of oxygen and carbon dioxide by diffusion

Adaptations for diffusion

large surface area, thin membrane, good blood supply, ventilation (in organisms)

Root hair cell

specialised cell with large surface area for absorbing water and mineral ions

Mineral ions

dissolved substances absorbed by plants, often by active transport

Water potential

measure of the tendency of water to move; water moves from higher to lower water potential

Turgid

plant cell swollen with water, membrane pressed against cell wall

Flaccid

plant cell that has lost water, less firm

Plasmolysed

plant cell where membrane pulls away from cell wall due to water loss

Isotonic

solution with equal water concentration to the cell (no net movement)

Hypotonic

solution with higher water concentration than the cell (water enters cell)

Hypertonic

solution with lower water concentration than the cell (water leaves cell)

Net movement

overall movement of particles in one direction

Equilibrium

point where there is no net movement of particles

Absorption

uptake of substances into cells or organisms